Safety device fob furnaces



Jan. 3, 1950 A. WILLETT SAFETY DEVICE FOR FURNACES Filed April 27, 1945$74M N k M f-i 4 4) i Patented Jan. 3, 1950 UNITED STATES PATENT OFFICESAFETY DEVICE FOR FURNACES Anthony Willett, Cleveland, Ohio ApplicationApril 27, 1945, Serial No. 590,633

3 Claims.

This invention relates to safety devices for furnaces, and moreparticularly to a device for automatically closing the draft door of afurnace or other heating unit when it becomes overheated. These,therefore, are the general objects of the present invention.

Heating plants, particularly hot air furnaces often become overheateddue to foregetfulness or neglect to close the draft door. Sometimes thedraft door remains open because of a failure in the power supply for anelectrical control of the furnace. In either instance the overheating ofthe furnace is a dangerous condition and may result in loss of thebuilding in which the heating plant is installed. Therefore, one of theobjects of the present invention is to provide an improved, eflicientand positive actin safety device which will cause the closing of thedraft door whenever the furnace temperature exceeds a predeterminedmaximum.

Another object of this invention is to provide a safety device which maybe manufactured at low cost, readily installed on existing furnacecontrol mechanisms, and which will not effect the operation of anexisting control mechanism unless the furnace becomes overheated.

A more specific object of the present invention is to provide a safetydevice for closing the draft door of a furnace whenever the furnacetemperature increases above a predetermined maximum and which device maybe readily reset to its normal position without a replacement of any ofits component parts, whenever the temperature of the furnace decreasesbelow the danger point.

Other objects and advantages of the inven tion will become more apparentfrom the following description, reference being had to the accompanyingdrawings illustrating a preferred embodiment of the invention. The novelfeatures of the invention are summarized in the claims.

In the drawings, Fig. 1 is a more or less diagrammatic illustration of afurnace havin my improved safety device incorporated in the draftcontrol system; Fig. 2 is a plan view of my improved safety device,partially in section to more clearly illustrate the internalconstruction thereof; Figs. 3 and 4 are sectional views through thedevice, the planes of the section being indicated by the correspondinglynumbered lines on Fig. 2.

Referring now to the drawings in detail, and particularly to Fig. 1, itwill be seen that I have illustrated a furnace I!) of the usualconstruction as being provided with a draft door H,

hinged at I! so as to close under the influence of gravity. The draftdoor is opened by a flexible unit, such as for instance a chain M. Thechain i4 is secured to the draft door, as at I5, and extends upwardly toa sheave l6, and then is looped downwardly around a sheave I1 which iscarried by the safety device, thence upwardly, as at Hi, to a suitablecontrol, either manual or automatic, as is well known My improved safetydevice comprises a housing 20 arranged to be secured to the outer casingIQ of the furnace by suitable screws or bolts passing through openings2| in the housing. The outer casing l9 of the furnace may be broken awaybeneath the device or the device may be applied directly to such casingif desired. The sheave I1 is connected to the device by a short chain24, at the end of which is a ring 25 arranged to be slid onto a lever26, pivoted as at 21, to the housing 20. This lever is normally held inthe position shown in full lines in Fig. 3 by a second lever or beam 28.The lever 28 is pivoted as at 29, to a bracket 30 formed on the housing20, and is normally locked in the position shown in full lines on Fig. 4by a spring-pressed latch member 3|. This latch is pivoted, as at 32, tothe housing 20, and is normally urged into engagement with the lever 28by spring 33.

Mounted within the housing 20 is a thermally responsive member 35. Asshown, this member comprises .a coiled strip of bi-metallicconstruction. One end of the strip is clamped to a bracket 36 whichprojects inwardly from the housing 29 by a clamp 31 which is secured inplace by screws 38. The innermost end 40 of the bi-metallic coil passesthrough a slot 4| in a vertically extending post 42 and is clampedtherein by a set screw 43. This post 42 passes upwardly, freely throughan opening 44 in the housin 20, and has an arm 46 secured to its upperend. As shown in Figs. 2, 3 and 4, the arm 46 comprises a bent metalstrip which is wrapped around the post 42 and clamped thereto by a bolt41, thus enabling the relative position of the arm on the shaft to bereadily adjusted.

The arm 46 is so adjusted relative to the latch 3i and the bi-metallicmember that when the furnace becomes heated to a predetermined degreethe action of the bi-metallic member will cause the arm 46 to swing in aclockwise direction (Fig. 2) and swing the latch from the fulllineposition shown in Fig. 4 to the dotted line position therein shown.-Whereupon, the weight of the draft door, through the flexible member orchain l4, will rock the arms 28 and 26 about their respective pivots tothe dotted line positions shown in Figs. 3 and 4, thus freeing the ring25 from the member 26 and increasing the effective length of the chain[4, thus permitting the draft door to drop to a closed position.

From the foregoing description, it will be seen that I have provided anextremely simple device which is positive in its action .and which willinsure the closing of the draft door whenever the temperature of thefurnace exceeds a predetermined maximum. Likewise, it will be noted thatin my improved construction, the latch mechanism, if reengaged while thetemperature of the furnace exceeds the predetermined maximum willimmediately be forced outof-engagebracket. andextending across saidsupport, a second bracket secured to and extending upward from saidsupport, a lever having one end pivoted to said last named bracket andextending substantially at right angles to and across said arm at apoint remote from the pivot thereof ment by the action of thebi-metallic member;

Likewise, it will be noted that when the furnace temperature drops belowthe danger point, the latch mechanism may be reset to its normalposition without requiring the replacement of any parts thereof, andthus may be used over and over again. a

I claim:

1. In a trip release mechanism, a support, an arm pivoted to saidsupport and extending thereacross, a second arm pivoted. to said supportand extending across said first'named arm at a point remote from thepivot thereof to prevent movement of the first named arm away from saidsupport, a ring slidably embracing said first named arm intermediate thepivot thereof and the second named arm, a releasable latch engaging saidsecond named arm to prevent movement thereof away from said first namedarm, resilient means to retain said latch in latching engagement withsaid second named arm, and movable means to trip said latch and permitthe release of said ring.

2. In a trip release mechanism, a support, an arm pivoted at one end tosaid support and extending thereacross, a lever having one end pivotedto said support and extending across and substantially at right anglesto and across said arm at a point remote from. the pivot thereof toprevent movement of said arm away from said support, a ringslidablyembracing said arm intermediate the pivot thereof and said leverwhereby the sliding movement, of said ring is restricted by engagementwith said lever, a pivoted latch overlaying the other end of said lever,resilient means to retain said latch in latching engagement with saidlever, means movable to engage and swing said latch away from said leverto permit release of said ring consequent upon upward tensicning of saidring, said means being movable to a position out of engagement with saidlatch, said lever and arm being free to swing toward said support underthe influence of gravity in the absence of upward tension applied tosaid ring and unattended by the release of said ring, whereby consequentupon the release of said latch by engagement therewith of said meansunattended by tensioning of said to prevent movement of the arm awayfrom said support, a ring slidably embracing said arm intermediate thepivot thereof and said lever whereby movement of said ring along saidfirst named arm is restricted by said first named bracket and saidlever, a pivoted latch overlaying the other end of said lever, resilientmeans to retain said. latch in latching engagement with said lever, andthermally responsive means carried by said support. and operative toengage and swing said latch away from said arm to permit release of saidring consequent upon upward tensioning of said ring and to move out of.engagement' with said latch, said arm and lever each being free toswing toward said support under the influence of gravity in the absenceof upward tension applied to said ring without releasing said ring,whereby following upon the release of said latch by said thermallyresponsive means unattended by the application of tension to said ringthe latch will return to its latching position and prevent release ofsaid ring consequent upon a subsequent application of a tensioning forcethereto unattended by a latch engaging movement of the thermallyresponsive means.

ANTHONY WILLETT.

- REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

